The ovens of the hot air-circulating type which have so far been available on the market cause no problem when used for a primary fermentation process in breadmaking wherein a dough is aerated, rounded and allowed to stand under a wet cloth in a pan for about an hour, but they cause problems when used for a subsequent secondary fermentation process in which the dough is degassed, divided and molded into easily ingestable pieces and allowed to stand for 15 to 20 minutes and further allowed to ferment for about 30 minutes. In the latter process, the surface of the bread tends to dry up under the influence of circulating hot air currents so that the final bread has many cracks in the crust and is case-hardened, thus detracting a great deal from its eating quality. If, to avoid such results, the surface of the bread is moistened with a spray of water in the course of the secondary fermentation, a good quality bread can be obtained provided that the water is added in an optimal fashion. However, if the moisture so added is excessive or inadequate, the finished bread varies widely in taste and shape. Therefore, the use of a water spray is difficult in a commercial application. Therefore, the hitherto-available hot air-circulating ovens having the fermentation capability have been additionally provided with upper and lower heaters, or in the case of the so-called oven range which is a combination of hot air circulating cooking means with high frequency heating means, high frequency waves of low output have been utilized for fermentation. These techniques, however, have the disadvantages of high cost, and because heating by highfrequency energy is germicidal, the latter method reduces the viable count of yeast organisms and, hence, fails to permit adequate fermentation.